Support substrate for integrated circuit chip adapted to be placed in a mould

ABSTRACT

Substrate, in particular a multilayer substrate constituting a mounting and electrical-connection support, having a face ( 2 ) for mounting at least one integrated-circuit chip ( 3 ) and capable of being placed, provided with this chip, in an injection mould ( 8 ) having two parts which take between them the periphery of the substrate and one of which defines a cavity ( 15 ) for moulding an encapsulation material for the purpose of encapsulating the said chip and has a face for bearing on the said mounting face, in which at least one recess ( 16 ) is provided, the said recess defining, above the said mounting face, a slot ( 17 ) constituting a vent for venting gases. Its aforementioned mounting face ( 2 ) has a region on which a metal outer layer ( 6 ) is placed, this layer being placed so as to extend along the said recess ( 16 ) and on the said bearing face ( 12 ) on either side of this recess.

[0001] The present invention relates to a substrate, in particular anorganic substrate, intended to support at least one integrated-circuitchip and suitable for being placed in an injection mould so as toencapsulate this chip in an encapsulation material in order toconstitute a package.

[0002] According to a known technique, rows of chips are mounted on acommon substrate so as to be encapsulated in a block of encapsulationmaterial, the whole assembly then being sawn so as to constituteindividual packages each containing a chip.

[0003] Usually, the injection moulds include vents made in the form ofslots above the face for mounting the chips on the substrates, whichvents serve for venting the gases during the operation of injecting theencapsulation material. The width of these slots is determined accordingto the encapsulation material to be injected and more particularlyaccording to the dimensions of the filler particles in thisencapsulation material. The tendency is to provide slots whose width isbecoming narrower and narrower so that the venting of gases duringinjection of the encapsulation material is becoming increasinglydifficult, especially when the mounting face of the substrates iscovered with a varnish.

[0004] The object of the present invention is to improve the venting ofgases during the operation of injecting the encapsulation material whileat the same time reducing the width of the gas venting slots.

[0005] The substrate according to the invention, in particular amultilayer organic substrate constituting a mounting andelectrical-connection support, has a face for mounting at least oneintegrated-circuit chip and is capable of being placed, provided withthis chip, in an injection mould having two parts taking between themthe periphery of the substrate, one of which determines a cavity formoulding an encapsulation material for the purpose of encapsulating thesaid chip and has a face for bearing on the said mounting face, in whichat least one recess is made, the said recess defining a slotconstituting a vent for venting gases.

[0006] According to the invention, the mounting face of theaforementioned substrate has a region on which a metal outer layer isprovided, the said layer being placed so as to extend along the saidrecess and onto the said bearing face on either side of this recess.

[0007] According to the invention, the said metal layer preferablyconstitutes a strip which extends so as to at least cover the saidrecess completely.

[0008] According to the invention, the said metal layer preferablyextends without interruption.

[0009] According to the invention, the said metal layer may be addedonto the said region.

[0010] According to the invention, the said metal layer could also beintegrated into the said region.

[0011] According to the invention, the mounting face of the substratemay advantageously be covered with a varnish layer which does not coverthe said metal layer.

[0012] According to the invention, the said metal outer layer preferablyextends to the outside of the region covered by the said chip.

[0013] According to the invention, the said substrate is suitable formounting at least one row of spaced-apart chips and the said metal outerlayer extends along this row.

[0014] The present invention will become more clearly understood onstudying a substrate suitable for being placed in an injection mould soas to encapsulate integrated-circuit chips mounted on this substrate,described by way of non-limiting example and illustrated by the drawingin which:

[0015]FIG. 1 shows a top view of a substrate according to the presentinvention, provided with rows of integrated-circuit chips;

[0016]FIG. 2 shows an enlarged partial sectional view on II-II of anedge of the substrate in FIG. 1;

[0017]FIG. 3 shows a cross section of an injection mould suitable foraccommodating the aforementioned substrate provided with chips; and

[0018]FIG. 4 shows a longitudinal partial section on IV-IV of theinjection mould in FIG. 3.

[0019] Referring in particular to FIGS. 1 and 2, these show a substrate1 in the form of a rectangular plate, in particular an organic substratein the form of a multilayer strip, which has a face 2 for mounting amultiplicity of integrated-circuit chips 3.

[0020] In the example shown, and in a manner known per se, the chips 3are grouped together so as to form four packets 4 spaced apart anddistributed over the length of the substrate 1, each packet comprising amatrix of sixteen chips spaced apart and distributed so as to formlongitudinal rows and transverse rows. The chips 3 are attached to themounting face 2 by means of metal balls 3a which furthermore constituteconnections between these chips and an integrated connection network(not shown) on the substrate 1.

[0021] The substrate 1 has, on its mounting face 2, between itslongitudinal edge 5 and the first longitudinal row of chips 3 placed acertain distance from this edge, four regions on which metal outerlayers 6 are provided, which layers form longitudinal rectangular stripsextending, respectively, approximately over the length of the packets 4and to the outside of the region covered by the chips 3.

[0022] In one embodiment, the metal outer layers 6 may be added onto themounting face 6 before the chips 3 are attached. In another embodiment,the metal outer strips 6 may be formed during the process of fabricatingthe multilayer substrate 1.

[0023] As shown in FIG. 2, the mounting face 2 of the substrate 1 iscovered with an oxidation-resistant varnish layer 7, this varnish notcovering the surface of the metal outer layers 6.

[0024]FIGS. 3 and 4 show an injection mould 8 which comprises a lowerpart 9 and an upper part 10 which are suitable for bearing one againstthe other and which have for this purpose bearing surfaces 11 and 12.

[0025] The lower part 9 has a cavity 13 which is hollowed out in itsbearing face 11 and has dimensions so as to accommodate, flat, thesubstrate 1 provided with the chips 3, these chips being placed so as toface upwards and the metal outer layers 6 of the substrate 1 runningalong one longitudinal edge 14 of this cavity and facing upwards.

[0026] The upper part 10 of the mould 8 has, hollowed out in its bearingface 12, four flat cavities 15 formed in such a way that, when the upperpart 10 of the mould 8 is made to bear on its lower part 9, thesecavities 15 define injection moulding chambers enveloping, some distanceaway, the packets 4 of chips 3, the bearing face 12 of the upper part 10of the mould 1 bearing on the peripheral region of the mounting face 2of the substrate 1 and between the packets 4 of chips 3.

[0027] On its longitudinal side corresponding to the metal outer layers6 of the substrate 1, the bearing face 12 of the upper part 10 of themould 8 has a multiplicity of recesses 16 which define, above themounting face 2 of the substrate 1, slots 17 constituting vents forventing gases, the said slots opening, transversely to the substrate 1,on one side into the cavities 15 and on the other side to the outside.

[0028] More specifically, the recesses 16 defining the transverse slots17 and the metal outer layers 6 carried by the substrate 1 are placed,respectively, in such a way that these layers extend along the recesses16 and at least cover them and in such a way that they extend over thebearing face 15 on either side of the slots 17.

[0029] Advantageously, the metal outer layers 6 slightly extend into thecavities 15 in such a way that if the varnish layer 7 covering themounting face 2 of the substrate 1 projects slightly over the surface ofthese metal outer layers 6, this varnish layer 7 does not reach theslots 17.

[0030] On its opposite side to that having the recesses 17, the bearingface 12 of the upper part 10 of the mould 8 has a multiplicity ofrecesses 18 which define, above the mounting face 2 of the substrate 1,injection slots 19 which, on the one hand, open into the side of thecavities 14 and, on the other hand, are connected to a device forinjecting the encapsulation material.

[0031] It follows from the above description that, when an encapsulationmaterial is injected into the cavities 15 of the mould 1 via theinjection slots 19, the gases contained or appearing in the cavities 15may be vented via the slots 17 constituting vents even if these slotsare narrow.

[0032] This is because the gas venting vents 17 are perfectly defined,on the one hand, by the recesses 16 made in the bearing face 15 of theupper part 10 of the mould 8 and by the metal outer layers 6 provided onthe mounting face 2 of the substrate 1, independently of the surfacefinish of the mounting face 2 of the substrate 1 in its other regionsand independently of the varnish layer 7, the metal outer layers 6constituting as it were relatively rigid plates held in place correctlyon either side of the recesses 16 defining the slots 17.

[0033] The present invention is not limited to the example describedabove. Many alternative embodiments are possible without departing fromthe scope defined by the appended claims.

1. Substrate, in particular a multilayer organic substrate constituting a mounting and electrical-connection support, having a face for mounting at least one integrated-circuit chip and capable of being placed, provided with this chip, in an injection mould having two parts taking between them the periphery of the substrate, one of which determines a cavity for moulding an encapsulation material for the purpose of encapsulating the said chip and has a face for bearing on the said mounting face, in which at least one recess is made, the said recess defining a slot constituting a vent for venting gases, characterized in that its aforementioned mounting face (2) has a region on which a metal outer layer (6) is provided, the said layer being placed so as to extend along the said recess (16) and onto the said bearing face (12) on either side of this recess.
 2. Substrate according to claim 1, characterized in that the said metal layer (6) constitutes a strip which extends so as to at least cover the said recess completely.
 3. Substrate according to either of claims 1 and 2, characterized in that the said metal layer (6) extends without interruption.
 4. Substrate according to any one of the preceding claims, characterized it that the said metal layer (6) is added onto the said region.
 5. Substrate according to any one of the preceding claims, characterized in that the said metal layer (6) is integrated into the said region.
 6. Substrate according to any one of the preceding claims, characterized in that its mounting face (2) is covered with a varnish layer (7) which does not cover the said metal layer (6).
 7. Substrate according to any one of the preceding claims, characterized in that the said metal outer layer (6) extends to the outside of its region covered by the said chip (3).
 8. Substrate according to any one of the preceding claims, characterized in that it is suitable for mounting at least one row of spaced-apart chips (3) and in that the said metal outer layer (6) extends along this row. 